1. Field of the Invention
The invention concerns a device for fixing an additional device to a firearm. The invention in particular relates to a tip-up mounting unit for fastening a longitudinally adjustable stop with tight tolerance (free of play) and able to accommodate the ever-changing (recoil and spring-back) forces that occur on the engaging mechanism when shooting with automatic weapons.
2. Description of the Related Art
Scope mounts are used to assemble targeting devices, e.g., telescopes, on various firearms. Various types of mounts are known, including pivot mounts, claw mounts, fixed mounts, and tip-up mounts. Tip-up mounts are particularly common among the military types of scope mount. Especially popular are so-called Picatinny mounts, which have scope bases executed according to MIL-STD-1913. Therein the weapon is equipped with a Picatinny rail, which has transverse grooves for receiving a recoil lug. For manufacturing-technical reasons, these transverse grooves have relatively large tolerances in width (5.23 mm+0.23 mm). In the mass production of mounts it is thus not possible to precisely fit the recoil lugs to the transverse grooves. If the clamping force of the tip-up mount on the Picatinny rail is not enough, there results, as a consequence of the constantly changing forces when firing automatic weapons, a relative movement between the assembly and Picatinny rail due to the inertia of the mount plus telescopic sight. This leads to unwanted losses of accuracy when shooting, and a wearing-out of the assembly parts in the clamping area.
With a one-piece assembly, with only a single recoil lug, no way is yet know to compensate for this play. Two-piece assemblies, consisting of a front and a rear element, each of which being provided with a recoil lug, offer the possibility of engaging the recoil lugs in their respective grooves of the mount in opposing orientations, i.e., forwards and backwards. Therewith the free play can almost, but not completely, be ruled out. The securing of the mounting on the Picatinny rail is accordingly complicated. Moreover, when changing the assembly to a different Picatinny rail, the established precise positioning of the recoil lugs forwardly and rearwardly may no longer exist due to the tolerances of the groove widths.